Nearly all cell phone cameras in existence today are unable to provide optical zoom capability due to the form-factor limitations. Providing optical zoom requires large focal length lenses that make the thickness of smartphones too large for average consumers. This is why nearly all smartphones provide only digital zoom capabilities in their cameras, where the zoom effect comes only from digital methods and not optical methods.
Digital zoom methods generally consist of interpolation algorithms such as Bicubic interpolation, poly-phase interpolation, or other such methods. These digital zoom methods process only one frame at a time. The key issue with digital zoom algorithms is that for large zoom factors (such as 4x or higher), the artifacts and noise in the image, which are not objectionable without zoom, are amplified and enlarged by the interpolation algorithm. The resulting image quality is not acceptable to most users.
As described in U.S. patent application Ser. No. 14/690,046, titled “METHODOLOGY FOR GENERATING HIGH FIDELITY DIGITAL ZOOM FOR MOBILE PHONE CAMERAS,” it is possible to use multiple frames together to provide High Fidelity Digital Zoom—referred to as HiFi Zoom for Still Images in this disclosure. Such methods utilize multiple frames and rely on the fact that there is a small difference in position of the camera due to hand-shake to minimize the artifacts from digital interpolation, improve signal to noise ratio, improve clarity and sharpness of the video, perceived detail and overall perceptual quality of images. Such methods are very complex, and extending such methods to videos is not straightforward for someone skilled in the art.